Geometry-dependent electro-optical properties of rectangular-crater quantum rings with off-centered impurities under orthogonal electric and magnetic fields

The electro-optical properties of an off-centered donor impurity confined in realistically modeled rectangular-crater quantum rings under orthogonal electric and magnetic fields are theoretically investigated. The electronic states are obtained by numerically solving the two-dimensional effective-mass Schrödinger equation. Our results reveal an anomalous oscillatory Stark effect strongly dependent on the impurity position and on the morphology of the central crater. Oscillatory behavior in the optical absorption spectrum appears for square craters with rounded corners under a threading magnetic field, whereas these oscillations are strongly suppressed for rectangular craters or square craters with sharp corners. In these latter configurations, the absorption coefficient becomes nearly insensitive to variations of the external fields within certain ranges, producing regions of quasi-constant optical response. These findings highlight the key role of crater geometry in controlling the electronic and optical properties of donor-doped quantum rings.